Temperature dependence of the spectral line narrowing and photoluminescence of MEH-PPV

We present an investigation into the temperature dependence of the spectral line-narrowing (SLN) behaviour of poly[2-methoxy, 5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and correlate this with measurements of the photoluminescence (PL) spectra as a function of temperature. These measurements were made with films spun from tetrahydrofuran (THF) which is the preferred solvent for line narrowing, and from chlorobenzene (CB). We observe a blue shift in the peak position of the SLN as the temperature is increased from 77 to 277 K. The PL spectra show a similar trend; however, for films spun from both THF and CB the PL spectra deviate from the SLN data, especially at high temperatures. Possible explanations for the difference in behaviour of PL and SLN in films spun from the two solvents are discussed, including the role of conformational disorder.